A few days ago, finally, I got around to testing code uploading to ESP8266 controllers (as ESP-12E). This is not so easy like it is with Arduino and Wemos D1 Mini. 🙂
I decided to do everything on the breadboard. USB-TTL programmer on 3V (CP2102), two buttons to switch the controller to firmware mode. And the ESP-12 itself [hangs well] on wires.
In the photo: I turned on three DHT22 modules (temperature / humidity sensor) simultaneously to calibrate (and check) their accuracy. BTW, maximum discrepancies turned out to be no more than 1 degree.